A federal judge declared a same-sex marriage ban in deeply conservative Texas unconstitutional on Wednesday, but will allow the nation's second-most-populous state to enforce the law pending an appeal that will likely go to the U.S. Supreme Court.

Judge Orlando Garcia issued the preliminary injunction after two gay couples challenged a state constitutional amendment and a long-standing law. His ruling is the latest in a tangled web of lawsuits across the country expected to end up in the Supreme Court next year.

"Without a rational relation to a legitimate governmental purpose, state-imposed inequality can find no refuge in our United States Constitution," Garcia wrote. "These Texas laws deny plaintiffs access to the institution of marriage and its numerous rights, privileges, and responsibilities for the sole reason that Plaintiffs wish to be married to a person of the same sex."

Garcia said the couples are likely to win their case and the ban should be lifted, but said he would not enforce his ruling pending one by the 10th Circuit Court of Appeals, which already is hearing two other states' cases. He also will give Texas time to appeal to the Fifth Circuit Court of Appeals in New Orleans.

Garcia, appointed by President Bill Clinton, is the first judge in the conservative Fifth Circuit to reach such a decision. Texas Attorney General Greg Abbott, who also is the leading Republican candidate to succeed Gov. Rick Perry, promised to appeal the decision to the New Orleans court.

"This is an issue on which there are good, well-meaning people on both sides," Abbott said in a statement. "The U.S. Supreme Court has ruled over and over again that States have the authority to define and regulate marriage."

The ruling is the latest in a series of victories for gay rights activists following similar decisions in Utah, Oklahoma and Virginia. The U.S. Supreme Court put the Utah ruling on hold until the 10th Circuit can consider an appeal, and Garcia said he would respect that order as well.

Mark Phariss and Victor Holmes filed their federal civil rights lawsuit saying Texas' ban unconstitutionally denied them the fundamental right to marry because of their sexual orientation. Cleopatra De Leon and Nicole Dimetman filed a lawsuit saying Texas officials violated their rights by not recognizing their marriage conducted in a state where gay marriage is legal.

"Having been together almost 17 years, we look forward to the day when we can get married and when all gay Texans enjoy equal rights to marry as well," Phariss and Holmes said in a statement.